NEC PD75402A - Manual (Page 132)

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CHAPTER 5. PERIPHERAL HARDWARE FUNCTIONS
Remarks M : Output by master
S : Output by slave
After the slave receives the data length, if the transmissible data is equal to or greater than that
data length, the slave returns ACK. If the data is insufficient, ACK is not returned and an error is
generated.
When a data transfer is performed, the slave compares the SIO contents before and after the
transfer to check whether the data was correctly output onto the bus. If the SIO contents before and
after the transfer are different, ACK is not returned and an error is generated.
➁
WRITE, END and STOP commands
This command performs a data write to the slave. The write data length is variable between 1 and
256 bytes, and is specified as a parameter by the master. If 00H is specified as the data length, this
is interpreted as a 256-byte data transfer specification.
Fig. 5-55 WRITE & END Command Transfer Format
(iii) Command formats
The transfer format of each command is shown below.
➀
READ command
This command performs a read from the slave. The read data length is variable between 1 and
256 bytes, and is specified as a parameter by the master. If 00H is specified as the data length, this
is interpreted as a 256-byte data transfer specification.
Fig. 5-54 READ Command Transfer Format
M S
READ ACK
Command
M S
Data Length ACK
Data
S S
Data 0 ACK
Data
S S
Data N ACK
Data
Remarks M : Output by master
S : Output by slave
M
WRITE
Command
S
ACK Data Length
M S
ACK
Data
Data 0
M
Data
ACK
S M
Data N
Data
S
ACK
M
END
Command
S
ACK